Characterization of diene monomers as healing agents for autonomic damage repair

Abstract

For effective autonomic healing of damaged polymers and composites, it is essential to understand how the encapsulated healing agent behaves during and after cure. In this study, two different diene monomers [dicyclopentadiene (DCPD), 5-ethylidene-2-norbornene (ENB)] and their blends were investigated as candidate self-healing agents, using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). DSC experiments for samples showed that DCPD has a melting transition while the blends and ENB have no melting in the temperature range measured. Samples for DMA were prepared and tested by two different methods in the presence of Grubbs catalyst. In the first case (method I), monomers were mixed with the catalyst directly. In the second case (method II), the catalyst was mixed with an epoxy/amine system and cured into a film that was polished to expose the catalyst. The cure behavior of monomer samples was examined on the epoxy/catalyst film. Method II is considered to be a simulative experiment, which can occur in a real situation for damaged epoxy matrix composite. It was found that acceleration of cure reaction and reduction of catalyst concentration is possible by blending DCPD with ENB from method I. Storage modulus (G') value after cure in method II showed that a DCPD: ENB blend ratio of 1:3 reached the highest G' value at shorter cure time and lower catalyst levels than other monomer combinations. DCPD and ENB are presumably responsible for increases in rigidity and reactivity, respectively. This may improve the healing efficiency in autonomic damage repairing applications. (c) 2006 Wiley Periodicals, Inc.